In the manufacture of buttons and the like thread holes or eyes are placed in the center of the button. These holes, however, may be partially or totally filled by a web or flash of material or they may off-set relative to the desired position. In addition to misplacement of the holes, one or more holes may be entirely missing from the button. Buttons with these common flaws are unsuitable for use in the manufacture of clothing because they cause breakdowns in the threading mahinery used by the clothing manufacturers. Additional defects such as cracks, chips, eccentricity of the button render the buttons unsuitable for use. Accordingly, it is necessary that all of the buttons manufactured be inspected for possible defects, and those that are found to be defective be separated from those that are acceptable for their intended purpose.
Generally, buttons are inspected and sorted by inspectors who sit along a conveyor belt and pick out the occasional bad buttons from thousands of buttons on the line. This type of inspection, however, is generally unproductive because the effectiveness of the sorters is a relatively short duration. Moreover, buttons manufactured from clear or translucent plastics that have small defects such as improper positioning of the openings or flashing therein, cracks and the like are difficult to distinguish from acceptable buttons on a rapidly moving assembly conveyor belt. Notwithstanding numerous methods and apparatus that have been proposed or attempted for inspecting plastic molded articles such as buttons and the like, including U.S. Pat. Nos. 2,332,308 and 2,351,702, the manual method of inspecting and sorting is still widely employed.
Advances in optical and/or optical-electrical scanning procedures have not produced satisfactory results when employed in a high-speed button manufacturing line. Recently, however, a button inspecting system has been devised taking advantage of laser technology and high-speed computers. With this system, the buttons positioned on the conveyor are scanned by the laser and the diffracted light from each of the rapidly scanned buttons is focused through a lens onto a photodetector. The diffraction pattern detected by the photosensor converts the signals into electrical data that the computer can analyze and compare on the basis of information stored within its memory. While this method provides highly reliable sorting information, it is relatively expensive, because of the computer and laser hardware utilized in the system, and difficult to combine with mechanical sorting means that are responsive to the system at the rate for which the system was designed to operate.
Accordingly, it is an object of the present invention to provide a method and apparatus for rapidly inspecting buttons. It is a further object of the invention to provide a sorting means responsive to the inspection apparatus means of the present invention for sorting defective buttons from those that are acceptable.